Physical features of the Wensum Valley

The main geological characteristics of Norfolk are relatively recent in origin. The strata dip gently down from west to east giving rise to outcropping of the series in the west along a north-south axis.

Most of the Wensum Valley is underlain by Upper Chalk, a white soft rock containing many large, irregularly-shaped, flinty nodules. Downstream of Lenwade, marine and sometimes shelly sands and gravels (Norwich Crag) were laid down above the chalk by a North Sea, which came further inland than it does today. These sands and gravels are almost entirely uncemented and resemble outwash glacial deposits, which were subsequently laid down during the Ice Ages.

Chalky boulder clay was carried eastward across Norfolk by the movement of glaciers during the Quaternary Era. This overlays the chalk above much of the upper half of the Wensum Valley. Glacial sands and gravels were also brought down by the ice and deposited along the river channel. These drift deposits, together with the later alluvial sediments laid down over the floodplain,

have a strong influence on the soils in the Valley, which have significantly influenced both the early colonisation by man and the development of agriculture in the area.

The good quality glacial sand and gravel deposits along the valley floor and lower sides have given rise to numerous mineral workings along the Wensum, with the stretch of river between Fakenham and Lenwade providing the highest concentration of active and worked pits. Due to the high water table on the floodplain, a ribbon of small and large lakes have formed which echo the course of the river channel.

The soils in the Wensum Valley are generally classified as grades 3 and 4.

On the valley floor the soils are mainly alluvial and poorly drained. The water table is high and permanent pasture is the most common land use. Most of these soils are grade 4.

Two main types of soils are found on the valley sides and top:

Upstream of Lenwade, the boulder clay predominates, giving heavy, poorly drained land with a flinty, sandy clay loam topsoil over a mottled brown clay.

Downstream of Lenwade, the Wensum Sands lie west of Norwich. These are outwash deposits with the rolling topography around Ringland having well-drained soils.